1. Field of the Invention
The present invention relates to a silicone rubber based pressure sensitive adhesive sheet which has slight pressure sensitive-adhesiveness, and is excellent in removability and which has high holding power.
2. Description of the Related Arts
Accompanying the development and advancement of information industries and electronic technology in recent years, display units such as CRT displays, liquid crystal displays, plasma displays and the like have come to be widely employed, including not only TV sets and personal computers but also copying machinery, facsimiles, watches/clocks, telephones.
It is a general practice to stick on a display screen in any of these display units, a protective film for the purpose of protecting the surfaces of the screen from breakage and/or scratch on impact; or a functional film for the purpose of imparting such functions as anti-reflection, antistatic property, antifoulancy, antiglare and the like.
There is formed on any of the above-mentioned various films, a pressure sensitive adhesive layer composed of a pressure sensitive adhesive such as an acrylic pressure sensitive adhesive. The pressure sensitive adhesive layer composed of an ordinary used pressure sensitive adhesive involves the problem of difficulty in exhibiting sufficient holding power at the time of repetitive sticking, since upon peeling off, the shape of an adherend remains un-removed on the surface of the pressure sensitive adhesive layer, and thus the surface fails to restore to the original flat state, or considerable period of time is required in restoring to the flat state.
On the contrary, a silicone rubber based pressure sensitive adhesive sheet wherein a silicone rubber layer is formed on the surface of a transparent substrate film is used as a protective sheet alone or in combination with anyone of a variety of functional films, because the silicone rubber layer is imparted with an excellent cushioning property.
The silicone rubber layer of the silicone rubber based pressure sensitive adhesive sheet is composed of silicone rubber which is usually blended with polysiloxane, a catalyst, a cross-linking agent and in addition an additive such as an adhesion improving agent or the like used for the purpose of improving adhesiveness to a substrate film (for instance, refer to Japanese Patent Application Laid-Open No. 56694/2000 (Heisei 12)).
However, since the blending of such an additive increases the adhesiveness of the silicone rubber, it has been necessary from a practical aspect to use a releasing film which is subjected to a releasing treatment with an expensive fluorine base material.